Good for you. Lots of fun and good shooting are ahead of you in the world of BP firearms.
I like the Remington 1858 (New Police) in .36 cal. Great shooter.
I also recommend the Lyman Great Plains flintlock. It may be the best production flintlock on the market. Properly primed (which means not too much priming powder - I remember that I was very surprised, and pleased, to discover how little is needed to make the gun go Bang.) it will shoot as described above - no noticeable delay. Squeeze trigger/Bang!
The process of discovering what load works best in a flintlock is no more difficult than determining what loads or cartridges any rifle shoots best.
And then there are those beautiful custom "made just for you" guns....
Pete